Adhesion phenotypes of pigs of Chinese and Western breeds and a White Duroc-Erhualian crossbreed with regard to susceptibility to enterotoxigenic Escherichia coli with fimbrial adhesins K99, 987P, and F41

Abstract

To investigate adhesion phenotypes of pigs of Chinese and Western breeds and a specific crossbreed with regard to enterotoxigenic Escherichia coli (ETEC) with fimbrial adhesins K99 (F5), 987P (F6), and F41 (F7). Purebred 6- to 8-week-old pigs of 3 Western breeds introduced into China (n = 144) and 12 Chinese breeds (148) and 1,330 adult White Duroc-Erhualian crossbred pigs. Brush border preparations were prepared from jejunal specimens collected from each pig following euthanasia. Each preparation was incubated with ETEC strains that had fimbrial adhesins K99, 987R or F41; an ETEC K88(-) strain was used as a negative control sample. The mean number of brush border-bound bacteria in aliquots of the bacteria-brush border suspensions (determined via phase-contrast microscopy) was used to determine each pig's adhesion phenotype for ETEC K99, 987R and F41 strains; the phenotype was classified as adhesive (susceptible) if ≥ 10% of examined brush borders bound > 2 bacteria. Most purebred and crossbred pigs had nonadhesive phenotypes with regard to ETEC K99 and 987P strains. For the F41 strain, 34.9% and 65.1% of all purebred pigs had adhesive and nonadhesive phenotypes, respectively; among crossbred pigs, these values were 39.2% and 60.8%, respectively. The percentage of pigs with the F41 adhesive phenotype was higher among Western breeds than it was among Chinese breeds (38.9% vs 31.1%). Results suggested that the ETEC F41 strain, but not the K99 or 987P strain, might be a cause of diarrhea in 6- to 8-week-old pigs in China.